This invention relates to hemodiafiltration cartridges, hemodiafiltration apparatus and hemodiafiltration methods.
When the kidneys in mammals fail to remove metabolic waste products from the body, most of the other body organs soon fail also. The symptoms which develop are termed uremia and the severity of these symptoms is proportional to the retention in the blood of metabolic waste products ordinarily excreted by the kidneys, two of the most toxic waste products being urea and creatinine. Various other metabolic products which can accumulate in the bloodstream include polypeptides, phenols, amines, guanidine, and a variety of middle molecules in the molecular weight range of 500-3000 daltons. The kidneys also provide electrolyte balance in the body when functioning normally, excreting Na.sup.+, K.sup.+, H.sup.+, Mg.sub.++ Ca.sup.++, Cl.sup.-, HCO.sub.3.sup.-, PO.sub.4.sup.-3, etc. ions in excess of body needs. When kidney failure occurs, the metabolic waste products will not be excreted and the proper electrolyte balance will not be maintained.
Hemodialysis (dialysis of the blood outside of the body) removes solutes, such as creatinine and urea, from the blood by diffusion down a concentration gradient. The solutes diffuse across a semipermeable membrane into a second liquid. Ultrafiltration removes small and middle size solutes by convective mass transfer. Basically, hydrostatic pressure causes solutes as well as plasma water to pass through the wall of a semipermeable membrane. Hemodiafiltration utilizes both diffusive and convective mass transfer and thus is a combination of hemodialysis and ultrafiltration.
Plasma water lost from the blood during hemodiafiltration or ultrafiltration needs to be replaced, at least in part. This replacement of fluid with sterile, non-pyrogenic fluid is currently accomplished in many ways such as by: (1) intravenous infusion; (2) adding sterile fluid in line before or after the filter cartridge and before the patient's body; and (3) backfiltration of dialysate which has been sterilized by the use of filter equipment connected to the filter cartridge. These current fluid replacement methods have many drawbacks. Intravenous infusion or replacement of fluid loss in line before or after the filter cartridge require the use of expensive sterile materials. Connecting filter equipment to the filter cartridge requires the use of bulky filter equipment and problems have occurred with providing a sterile and non-pyrogenic dialysate transfer.
Accordingly, the principal object of this invention is to provide a hemodiafiltration apparatus which has the capability of replacing lost fluid in the patient with sterile and non-pyrogenic dialysate without the use of additional filter equipment for dialysate treatment and without the use of expensive sterile materials.
It is a further object of the invention to provide a hemodiafiltration cartridge for said hemodiafiltration apparatus that has traditional connectors for blood and dialysate and thus can be used with standard dialysis apparatus.
It is still a further object of the invention to provide such a hemodiafiltration apparatus which is quite efficient in terms of time and expense.